Tony Blair has declared war on the UK's hereditary peers. The skirmishing is over and the government has started to set about consigning more than 700 hereditaries to the history books.

Some of them may earn a temporary reprieve under a deal done with the Conservatives, but by the time of the next general election it is likely that not a single hereditary peer will remain in the Lords - ending 600 years of tradition.

Labour sees the reform as a means of stopping the Tories' historic domination of the Lords.

Once the government details its bill to abolish hereditaries, a royal commission will begin looking into the future make-up of the Lords.

But what the government wants to do once the hereditaries have gone is far from clear.

Who sits in the new house, how they get there and what their duties will be are all up for grabs.

Prudent evolution

The Lord Chancellor, Lord Irvine - one of the key figures at the heart of the government's plans to modernise the UK's democracy - says whatever is finally proposed will be a "prudent and responsive move to ensure the smooth evolution of the constitution".

Lord Irvine favours reform based on "principled pragmatism"

But if the government is not exactly sure what it hopes to see once the all-new House of Lords is up and running there are plenty of people who have ideas.

Many of the government's own backbenchers quietly favour a fully-elected second chamber, a move which was party policy up until 1992. It is a hope shared by the pro-democracy pressure group Charter 88.

Second chamber with bite

Greg Power, of Charter 88's Parliamentary Unit, told BBC News Online: "A second chamber whose membership is based on appointment and entitlement runs counter to all notions of democracy and as a result the House of Lords has very little public support or legitimacy."

He also sees the re-vamped upper house being a robust counter-weight to the Commons.

"I think if you are going to have a second chamber, it is there to question the House of Commons and it must have the power to delay and revise legislation.

"If you are not going to give it that power there's no point in having it."

'A Constitutional longstop'

Tory MP Andrew Tyrie agrees up to a point. He told BBC News Online: "We need a check on the over-mighty power of the government in the House of Commons which inevitably comes with a large majority.

"The upper house has got to have some legitimacy to question what happens in the Commons and it can only acquire that legitimacy, in my view, by having a democratic element put in there."

But he stops short of backing a fully-elected second chamber, instead preferring an upper house made up at least 50% elected members, the rest being appointed.

He adds the members of the new upper house "don't need to be elected as frequently as MPs".

MPs have the lion's share of power

He sees a system whereby each member would serve twice as long as an MP, in the hope that this would keep "them from the pressure of the whips and becoming part of the Commons machinery and give them a sense of perspective and distance to act as a constitutional long stop".

Labour's partners in constitutional reform, the Liberal Democrats, back a partly-elected upper chamber.

Lord Harris of Greenwich, although unwilling to be drawn on the party's views before it has submitted its evidence to the Royal Commission, said: "I think there is by and large some support [from Lib Dems] for a chamber which is partly elected and partly not elected."

He said his party was keen to see the Lords retain some of their traditional independence despite the injection of democracy: "We favour the house subsequent to the removal of the hereditaries as consisting of some cross-bench peers."

'Democracy means muscle'

Reform may lead to more Westminster clashes

What the House of Lords will look like once Labour has dealt with the hereditaries remains to be seen, but it is likely to take into account other recent changes to the UK's body politic, including devolution and the incorporation of the European Convention on Human Rights into UK law, but even a small increase in democracy is likely to see more wrangling between Commons and Lords.

As Meg Russell of University College London's Constitution Unit points out: "Directly-elected chambers have no fear about using their constitutional muscle in challenging the lower house whereas those which are indirectly elected or appointed tend to hold back even if they've got full powers because the lower house is clearly the more democratic one."

But a government that has seen its legislative programme frustrated by a rebellious upper house - which inflicted 39 defeats on Tony Blair in his first parliamentary session - may think twice before handing too much power to a reformed House of Lords.